Perspective is a term used to refer to the way in which objects, visual scenes, etc. appear to the human eye based on spatial attributes and/or the dimensions of such objects, visual scenes, etc., as well as the position of the human eye relative to those objects, visual scenes, etc. Since the Renaissance period, artists have used perspective as a way to depict three dimensional (3D) scenes onto a two dimensional (2D) surface. In the context of, e.g., photographic imaging, perspective may be adjusted or controlled depending on the positioning of the camera lens when a photograph is taken and/or by adjusting or controlling depth of field.
Oftentimes, unless a photographer is “perfectly” positioned, the perspective of a photograph taken by the photographer, especially one which includes buildings or other objects with straight lines and/or orthogonal aspects, is skewed. As an example, depending on where or how a photograph of, e.g., a building, is taken, one or more edges of the building that should be vertical may appear to be tilted or otherwise, non-vertical. Hence, post-processing tools or software, such as image editors, are used to manipulate the perspective in an image. However, conventional post-processing tools provide limited manipulation at best, such as, e.g., allowing manipulation only from the four corners of an entire image, and even those tools that do provide a mechanism for warping/controlling perspective often involve multiple tedious steps. That is, a user must actually work backwards to achieve a desired perspective, and must do so in the dark, i.e., without any preview of the adjusted perspective. In such instances, and for all intents and purposes, a user is forced to adjust perspective by trial and error without direct input, where, for example, the user specifies an area to be warped, inputs certain constraints or parameters, and then waits for the conventional tool to display the result.
Further to the above, conventional tools do not provide for direct image space controls over vanishing points, construction lines and object shapes that illustrators/artists/users commonly adjust to create perspective images. Moreover, these conventional tools limit photographers to using a single, consistent projection across an entire image. Unlike painters, photographers cannot create images from physically inaccessible viewpoints, or locally combine multiple perspectives for different objects.